1. Field of the Invention
This invention relates to a pneumatic sealant gun, and particularly to a changeable sizing assembly and a control assembly for the intake/exhaust of the sizing assembly.
2. Description of the Prior Art
The current sealant is usually made of silicone or epoxy; the silicone sealant is usually loaded in a cylindrical tube; the sealant made of epoxy includes a primary agent and a hardening agent, which are loaded in two cylindrical tubes respectively, being mixed up via a mixing tube before use. The main tube loaded with such sealant is mounted on a connecting base in front of a sealant gun; the sealant can be extruded out of the gun upon the gun trigger being pulled. Such a sealant gun has a very low working efficiency. Another kind of sealant gun has a control assembly to control a compressed air as a pushing force to extrude a sealant in a tube mounted in the front end of the gun. The control assembly includes a trigger, whereby the control function is to be performed. In the conventional sealant gun, a one-way air-supply assembly is used, and controlled with a trigger. Since there is no exhaust function in such a gun, a given volume of compressed air would be left in the gun after the trigger being released; as a result, the sealant in the sealant tube would be extruded out continuously before the residual compressed air being released completely; the aforesaid condition of a conventional sealant gun is deemed a drawback; Moreover, since the handle and the sealant tube of such a sealant gun are usually formed integrally into one piece, the handle is unable to be used for different types of sealant guns, if necessary.